The conventional concrete is produced by mixing three essential components: cement, water and aggregates, to which eventually a fourth component is added. This component is generically named as an additive, although the air is another component. Chemically, concrete is composed by the four most abundant substances on the crust of the earth (silicates, aluminates, iron and calcium components).
We can make clear that cement, one of the concrete components, was used since the beginning of the 800's and since then, the Portland cement has become the most worldwide used cement.
Cement mixture can be hydraulic when setting and hardening, as they chemically react with water; or they can be aerial, when they set and harden in contact with air.
In both cement mixtures, the initial desirable characteristics of the mixture or fresh concrete are: plasticity, moulding and easy compactibility. But this mortar will gradually turn rigid acquiring the aspect, behaviour and properties of a solid body forming the hardened concrete.
Consequently with this, the mechanical behavior and durability of this material in the service it offers, depends on three basic aspects:    1. The characteristics, composition and properties of the hardened cementing matrix: this implies the selection of an appropriate cement mixture, the use of a convenient relation water/cement of 0.2 to 0.4 and the eventually use of a necessary additive, with all of which it may result in a potentially safe quality.    2. The quality aggregates, according to the functions that the structure will perform, so that they do not represent the weak point in the behaviour of concrete and its capacity to resist adequately and for a long time to exposure and service conditions, to which it is submitted.    3. The cement matrix affinity with the aggregates and its capacity to work together, depends on the physical and chemical characteristics of the cement, the mineralogic and petrographic composition of the rocks that conform the aggregate and the form, maximum size of the particle and superficial texture of them.
Besides the physical characteristics, that contribute to the intrinsic quality of the concrete and that can be quantified, they are included: its mechanic resistance, elasticity, thermal properties and maximum particle size; which allow establishing the cement mixture quality according to the corresponding national and international standards (ASTM International). This is, the material utilized for the elaboration of the concrete affects the facility with which it can be poured and finished, it also affects the time it needs to harden, the resistance it can acquire and how well it covers the functions for which it was prepared.
The way in which each one of the components of the cement mixture contributes in its properties and particular characteristics are mentioned straight away. The different kinds and classes of cement affect the cohesion, workability, settling down and pouring at the time of hardening, mechanic resistance acquisition, heat generation, resistance against attack of sulfate, dimensional stability (volumetric changes) and the chemical stability (cement-aggregates reactions). In some aspects, the influence of the cement is fundamental, but in others it has a fewer importance because there are other factors that also influence and of which effects are more outstanding.
Water has two different applications as a concrete component: an internal one when it is used in the mixture and other external when concrete is “cured” with it. Although in this applications the water characteristics have different effects on the concrete, it is desirable to employ water of the same quality in both cases. The quality requirements for the water used in the concrete mixture has no obliged relation with the bacteriological aspect (as in case of drinkable water), basically it refers to its physicochemical characteristics and its effects over the properties of the concrete and behaviour. Upon the undesirable effects that can show up because of the use of inadequate water, they can appear in a short period of time (related with the hardening time and the initial resistances), in a medium period of time (with resistances after 28 or more days) and in a long term (can consist in attack for sulfate, the alkali-aggregate reaction and the scouring of the reinforcement steel). The quantity of water necessary for hardening, has a maximum proportion of 40% respect to the cement quantity. The supplementary or extra water can be in a proportion of almost a 30% more; it is not fixed and occupies certain volume in form of capillary pores in the hardened cementant mixture. The bigger the water excess presence there will be more capillaries quantity in the cement paste. When the total quantity of capillaries correspond to a water/cement relation (w/c)=0.7, the capillaries are so numerous that they are united between them forming a permeable net. In consequence, if you add 70 g water to 100 g cement (w/c=0.7), the first 20 g are chemically fixed, the following 20 g are fixed by adsortion and the remaining 30 g stay free in the capillary net.
In the conventional hydraulic concrete mixtures, the aggregates use to represent approximately between 60% and 75% of the absolute volume of all the components; that is why the remarkable influence that the aggregates characteristics and properties exert over the corresponding concrete. There are diverse materials that with certain frequency accompany the aggregate, and whose presence is inconvenient, for example: the undesirable fine materials (lime and clay), and organic matter (humus and small fragments of roots, plants or wood), among others.
The additive, is a different material to the water, the hydraulic cement aggregates and the reinforcement fibers, and it is added to the mortar immediately before or during the mixing (American Concrete Institute or ACI 116(26)). This is, the concrete additives are used for the fundamental purpose to modify, in a convenient way, the behaviour of the concrete in its fresh state, and/or induce or improve determined desirable properties in the hardened concrete. This will represent a lower cost because of energy saving, for example increasing the defense characteristics against freezing and thawing, the delay or acceleration of the hardening time and a very high resistance is obtained, to mention some.
Some of the cement mixture components can be organic, containing N and/or fat acids in their structures, can be thermoplastic that in general increase the tension force and its flexibility. As shown by the patents or patent requests: MX/A/2004/010631, WO2006/116387 A2, MX230744, MX221807, MX167038, PA/A/2006/005553, JP2004231497, JP2001213649, KR20010027978, ES2,030,845, JP11107459, RU2275342. Some cement mixtures hold elements to prevent scouring (MX154260, MX187569, PA/a/2006/005091, JP2004231497). Also, many other cement mixtures have been described (GB 2,398,296, JP2004224647, USRE37,655, MX/PA/A/2002/012612, U.S. Pat. No. 6,755,907, DE4324190, JP2003107025, JP4292447, JP9296033, MX 191331, PA/a/1999/008311, MX160941, PA/a/1999/02182, PA/a/1996/05755, MX241331, PA/a/1998/09713, MX253295, MX/A/2008/003801, WO1995/13995, WO01/14277).
Additives can be nanoparticles (US2008/0242769A1), can be antimicrobials (US 2008/0242769 A1), they can be granular, polymeric and/or water-soluble; all of which are added with the purpose of preventing contaminations, increasing flexibility, acoustic insulation and adhesivity, among others (MX 238915, JP8059325, ES2135634, CH679665, DE3436215, DE3143071, U.S. Pat. No. 3,042,608, U.S. Pat. No. 6,902,002). Other additives are made out of worn out materials (KR20030088716, ES2152197, DE19728164).
Particularly, in this patent request, dopamelanin and/or its precursors and/or its analogues and/or derivatives, is/are used as an additive, considering and taking advantage due to peculiar characteristics of this component.
Lets remember the extraordinary melanin and melanocite properties related to water (melanin, in presence of light, dissociates water); these properties have been glimpsed relatively short time ago; thus the publications that called the attention related to the theme initiated around 1996. Since 1997 it has been proposed (Solis Herrera, 1997), to utilize the unusual capacities of melanin molecule for diverse industrial processes, such as reusable energy generation, for medicinal purposes, and this document proposes the melanin utilization to improve the concrete qualities in the curing processes, improving its physical resistance qualities, flexibility without diminishing drastically its mechanic capacities (ductility) and scouring resistance, that cause loss in steel-concrete adherence and nominal diameter in the reinforcement steel, which in many cases is the cause of collapses, in more or less grade and in direct or indirect form.
Melanin posses chemical, biochemical and electronic properties that have not been clarified, detected, understood, or predicted in its whole; but one of them is that melanin generates molecular oxygen and hydrogen derivated from the water photolysis. This is based on the following reaction:2H2O2H2+O2+4e−
For this cause, to more the melanin, the concrete will dispose of a major quantity of molecular oxygen and hydrogen, as well as energy and high energy electrons to carry out diverse chemical reaction that regularly occurred in all the components, from which concrete is not the exception.